Mitigation of uplink/downlink assymetry

Abstract

An UL carrier frequency or a downlink carrier frequency is adapted as a consequence of a determination that there is a difference in link budgets between uplink and downlink. Since a downlink provides a geographical coverage that is of a certain size, a lesser reliability of the uplink has a consequence that a mobile terminal may not be able to communicate when located far from a network node that transmits the downlink but still within the geographical coverage area of the downlink. Such drawbacks of present day wireless communication systems can be at least mitigated by embodiments of the present disclosure.

The invention claimed is: 
     
       1. A method in a first node in a wireless communication system, the first node having a connection with a second node in the wireless communication system via an uplink, at a current UL carrier frequency and via a downlink (DL), at a current DL carrier frequency, the method comprising:
 determining a current link budget for the UL; 
 determining a current link budget for the DL; 
 calculating a current link budget difference between the current link budget for the UL and the current link budget for the DL; 
 if the current link budget difference is greater than a first threshold value, then performing an UL carrier balancing procedure that comprises:
 selecting, based on the current link budget difference, the current UL carrier frequency and a predetermined set of possible future UL carrier frequencies, a future UL carrier frequency for which the link budget difference value is below a second threshold value; and 
 changing the current UL carrier frequency such that the current UL carrier frequency is equal to the selected future UL carrier frequency. 
 
 
     
     
       2. The method of  claim 1 , wherein the selected future UL carrier frequency is lower than the current DL carrier frequency. 
     
     
       3. The method of  claim 1 , comprising:
 determining whether or not any of the current link budget for the UL and the current link budget for the DL is below a second threshold, and wherein: 
 the UL carrier balancing procedure is performed only if it is determined that any of the current link budget for the UL and the current link budget for the DL is below the second threshold. 
 
     
     
       4. The method of  claim 1 , comprising:
 transmitting a message on the current DL carrier frequency; and 
 receiving, on the current DL carrier frequency, an ACK message related to the transmitted message. 
 
     
     
       5. The method of  claim 1 , comprising:
 receiving a message on the current DL carrier frequency; 
 determining whether or not an acknowledgement (ACK) message is to be transmitted relating to the received message; and 
 if it is determined that an ACK message is to be transmitted, then transmitting the ACK on the current DL carrier frequency. 
 
     
     
       6. The method of  claim 1 , comprising:
 determining a respective available bandwidth for the predetermined possible future UL carrier frequencies; 
 determining a modulation and coding scheme (MCS) that is to be used in the connection via the UL; and 
 calculating a respective required signal to noise ratio (SNR) value based on the determined bandwidths and the determined MCS, and wherein: 
 the selection of a future UL carrier frequency is further based on the calculated required SNR values. 
 
     
     
       7. The method of  claim 1 , comprising:
 receiving a message on the current DL carrier frequency; 
 determining that an ACK message is to be transmitted and, as a consequence of the determination that an ACK message is to be transmitted; 
 determining a MCS of the received message on the current DL carrier frequency; 
 selecting, based at least in part on the determined MCS of the received message, a MCS for the ACK message; and 
 transmitting the ACK message on the current UL carrier frequency using the selected MCS. 
 
     
     
       8. The method of  claim 1 , comprising:
 receiving, from the second node, a plurality of test signals on a respective UL carrier frequency; and 
 determining information that is indicative of path loss for the received test signals, and wherein: 
 the selection of a future UL carrier frequency is further based on the information that is indicative of path loss for the received test signals. 
 
     
     
       9. A method in a first node in a wireless communication system, the first node having a connection with a second node in the wireless communication system via an uplink (UL), at a current UL carrier frequency and via a downlink (DL) at a current DL carrier frequency, the method comprising:
 determining a current link budget for the UL; 
 determining a current link budget for the DL; 
 calculating a current link budget difference between the current link budget for the UL and the current link budget for the DL; 
 if the current link budget difference is greater than a first threshold value, then performing a DL carrier balancing procedure that comprises:
 selecting, based on the current link budget difference, the current DL carrier frequency and a predetermined set of possible future DL carrier frequencies, a future DL carrier frequency for which the link budget difference value is below a second threshold value; and 
 changing the current DL carrier frequency such that the current DL carrier frequency is equal to the selected future DL carrier frequency. 
 
 
     
     
       10. The method of  claim 9 , wherein the selected future DL carrier frequency is higher than the current UL carrier frequency. 
     
     
       11. The method of  claim 9 , comprising:
 determining whether or not any of the current link budget for the UL and the current link budget for the DL is below a second threshold, and wherein: 
 the DL carrier balancing procedure is performed only if it is determined that any of the current link budget for the UL and the current link budget for the DL is below the second threshold. 
 
     
     
       12. A first node for use in a wireless communication system, the first node configured to have a connection with a second node in the wireless communication system via an uplink (UL) at a current UL carrier frequency and via a downlink (DL) at a current DL carrier frequency, the first node comprising radio frequency control circuitry, a processor and a memory, said memory containing instructions executable by said processor whereby said first node is operative to:
 determine a current link budget for the UL; 
 determine a current link budget for the DL; 
 calculate a current link budget difference between the current link budget for the UL and the current link budget for the DL; 
 if the current link budget difference is greater than a first threshold value, then perform an UL carrier balancing procedure that comprises:
 select, based on the current link budget difference, the current UL carrier frequency and a predetermined set of possible future UL carrier frequencies, a future UL carrier frequency for which the link budget difference value is below a second threshold value; and 
 change the current UL carrier frequency such that the current UL carrier frequency is equal to the selected future UL carrier frequency. 
 
 
     
     
       13. The first node of  claim 12 , operative such that the selected future UL carrier frequency is lower than the current DL carrier frequency. 
     
     
       14. The first node of  claim 12 , operative to:
 determine whether or not any of the current link budget for the UL and the current link budget for the DL is below a second threshold, and operative such that: 
 the UL carrier balancing procedure is performed only if it is determined that any of the current link budget for the UL and the current link budget for the DL is below the second threshold. 
 
     
     
       15. The first node of  claim 12 , operative to:
 transmit a message on the current DL carrier frequency; and 
 receive, on the current DL carrier frequency, an ACK message related to the transmitted message. 
 
     
     
       16. The first node of  claim 12 , operative to:
 receive a message on the current DL carrier frequency; 
 determine whether or not an acknowledgement (ACK) message is to be transmitted relating to the received message; and 
 if it is determined that an ACK message is to be transmitted, then transmit the ACK on the current DL carrier frequency. 
 
     
     
       17. The first node of  claim 12 , operative to:
 determine a respective available bandwidth for the predetermined possible future UL carrier frequencies; 
 determine a modulation and coding scheme, MCS, that is to be used in the connection via the UL; 
 calculate a respective required signal to noise ratio (SNR) value based on the determined bandwidths and the determined MCS, and operative such that: 
 the selection of a future UL carrier frequency is further based on the calculated required SNR values. 
 
     
     
       18. The first node of  claim 12 , operative to:
 receive a message on the current DL carrier frequency; 
 determine that an ACK message is to be transmitted and, as a consequence of the determination that an ACK message is to be transmitted; 
 determine a MCS of the received message on the current DL carrier frequency; 
 select, based at least in part on the determined MCS of the received message, a MCS for the ACK message; and 
 transmit the ACK message on the current UL carrier frequency using the selected MCS. 
 
     
     
       19. The first node of  claim 12 , operative to:
 receive, from the second node, a plurality of test signals on a respective UL carrier frequency; 
 determine information that is indicative of path loss for the received test signals, and operative such that: 
 the selection of a future UL carrier frequency is further based on the information that is indicative of path loss for the received test signals. 
 
     
     
       20. A first node for use in a wireless communication system, the first node configured to have a connection with a second node in the wireless communication system via an uplink (UL) at a current UL carrier frequency and via a downlink (DL) at a current DL carrier frequency, the first node comprising radio frequency control circuitry, a processor and a memory, said memory containing instructions executable by said processor whereby said first node is operative to:
 determine a current link budget for the UL; 
 determine a current link budget for the DL; 
 calculate a current link budget difference between the current link budget for the UL and the current link budget for the DL; 
 if the current link budget difference is greater than a first threshold value, then perform a DL carrier balancing procedure that comprises:
 select, based on the current link budget difference, the current DL carrier frequency and a predetermined set of possible future DL carrier frequencies, a future DL carrier frequency for which the link budget difference value is below a second threshold value; and 
 change the current DL carrier frequency such that the current DL carrier frequency is equal to the selected future DL carrier frequency. 
 
 
     
     
       21. The first node of  claim 20 , operative such that the selected future DL carrier frequency is higher than the current UL carrier frequency. 
     
     
       22. The first node of  claim 20 , operative to:
 determine whether or not any of the current link budget for the UL and the current link budget for the DL is below a second threshold, and operative such that: 
 the DL carrier balancing procedure is performed only if it is determined that any of the current link budget for the UL and the current link budget for the DL is below the second threshold. 
 
     
     
       23. A non-transitory computer readable storage medium comprising computer program instructions which, when executed on at least one processor in a first node, cause the first node to carry out a method in a wireless communication system, the first node having a connection with a second node in the wireless communication system via an uplink (UL) at a current UL carrier frequency and via a downlink (DL) at a current DL carrier frequency, the method comprising:
 determining a current link budget for the UL; 
 determining a current link budget for the DL; 
 calculating a current link budget difference between the current link budget for the UL and the current link budget for the DL; 
 if the current link budget difference is greater than a first threshold value, then performing an UL carrier balancing procedure that comprises:
 selecting, based on the current link budget difference, the current UL carrier frequency and a predetermined set of possible future UL carrier frequencies, a future UL carrier frequency for which the link budget difference value is below a second threshold value; and 
 changing the current UL carrier frequency such that the current UL carrier frequency is equal to the selected future UL carrier frequency. 
 
 
     
     
       24. A non-transitory computer readable storage medium comprising computer program instructions which, when executed on at least one processor in a first node, cause the first node to carry out a method in a wireless communication system, the first node having a connection with a second node in the wireless communication system via an uplink (UL) at a current UL carrier frequency and via a downlink (DL) at a current DL carrier frequency, the method comprising:
 determining a current link budget for the UL; 
 determining a current link budget for the DL; 
 calculating a current link budget difference between the current link budget for the UL and the current link budget for the DL; 
 if the current link budget difference is greater than a first threshold value, then performing a DL carrier balancing procedure that comprises:
 selecting, based on the current link budget difference, the current DL carrier frequency and a predetermined set of possible future DL carrier frequencies, a future DL carrier frequency for which the link budget difference value is below a second threshold value; and 
 changing the current DL carrier frequency such that the current DL carrier frequency is equal to the selected future DL carrier frequency.